Method and apparatus for recovering video color subcarrier signal
First Claim
1. A method for generating a video clocking signal, comprising:
- producing an output video clocking signal from an oscillator;
receiving a reference video signal;
generating a first error signal by comparing a first aspect of said reference video signal with a first aspect of said output video clocking signal;
generating a second error signal by comparing a second aspect of said video reference signal with a second aspect of said video clocking output signal, generating a horizontal sync signal from a counter, generating weighted sampling factors, and producing a product of weighted sampling factors and the horizontal sync signal; and
adjusting said oscillator using the first error signal and the second error signal.
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Abstract
An embodiment of the present invention provides a signal generator for generating a signal with a predetermined frequency. The signal generator includes a first comparator for generating a first error signal and a second comparator for generating a second error signal. The first and second comparators are coupled to an oscillator configured to receive the first and second error signals and generate the signal having a predetermined frequency. Another embodiment of the present invention provides a signal generator for generating a signal with a predetermined frequency. The signal generator includes a counter for generating a first count, Q_last. The counter is coupled to a ratio counter which generates a signal having a value less than or equal to Q_last. The contents of the ratio counter represent the phase of the signal having a predetermined frequency. The ratio counter outputs the signal having a predetermined frequency.
57 Citations
13 Claims
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1. A method for generating a video clocking signal, comprising:
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producing an output video clocking signal from an oscillator;
receiving a reference video signal;
generating a first error signal by comparing a first aspect of said reference video signal with a first aspect of said output video clocking signal;
generating a second error signal by comparing a second aspect of said video reference signal with a second aspect of said video clocking output signal, generating a horizontal sync signal from a counter, generating weighted sampling factors, and producing a product of weighted sampling factors and the horizontal sync signal; and
adjusting said oscillator using the first error signal and the second error signal. - View Dependent Claims (2, 3)
the second aspect of said video clocking signal is the phase of a generated horizontal sync signal;
the second aspect of said reference video signal is the phase of the horizontal sync signal from the counter; and
the second error signal is an accumulated value which becomes a positive value if the generated horizontal sync signal is behind the horizontal sync signal from the counter, and becomes a negative value if the generated horizontal sync signal is ahead of the horizontal sync signal generated from the counter.
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3. The signal generator of claim 1, wherein a multiple of the video clocking signal is used to sample the reference video signal.
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4. An apparatus comprising:
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a horizontal sync comparator receiving a reference horizontal sync signal and a generated horizontal sync signal, and generating a horizontal sync error signal, said horizontal sync comparator comprising;
a weighted sampling factors ROM coupled to the pixel counter and configured to generate weighting factors, a multiplier coupled to the weighted sampling factors ROM and configured to generate a product of the weighting factors and the reference horizontal sync signal, and an accumulator coupled to the multiplier and configured to generate the horizontal sync error signal; and
a digitally controlled oscillator coupled to the horizontal sync comparator to receive the horizontal sync error signal and to generate an output signal. - View Dependent Claims (5, 6, 7, 8)
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9. A video signal generator, said video signal generator comprising:
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a fixed pixel clock generator;
a counter coupled to said fixed pixel clock generator, said counter to count a number of pixels during each horizontal scan line of a reference video signal;
a ratio counter coupled to the counter, the ratio counter to generate a phase signal; and
a phase to amplitude converter, said phase to amplitude converter receiving said phase signal to generate an output color subcarrier signal. - View Dependent Claims (10, 11, 12, 13)
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Specification